This application claims the benefit of Korean Patent Application Nos. 98-22716 filed Jul. 10, 1998 and 98-44230 filed on Oct. 21, 1998, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method of crystallizing an amorphous silicon layer and a crystallizing apparatus thereof in which the amorphous silicon layer is crystallized by using plasma.
2. Discussion of Related Art
In view of performance, low temperature polysilicon, of which product cost is low owing to its low formation temperature and which also provides wide image area, is as good as high temperature polysilicon. There are various methods for forming low temperature polysilicon, such as solid phase crystallization, laser crystallization and the like.
When providing low temperature crystallization under 400xc2x0 C., which is disclosed in Hiroyaki Kuriyama, et al., Jpn. J Appl. Phys., 31, 4550 (1992), the laser crystallization fails to provide uniform crystallization and has difficulty in forming polysilicon on a substrate having a wide area due to an expensive apparatus and low productivity.
When polysilicon is formed by solid phase crystallization, uniform crystals are provided by using an inexpensive apparatus. However, the solid phase crystallization requires high temperature and long crystallization processing time. Such process is seldomly applied to forming polysilicon on a glass substrate and has low productivity.
A new method of crystallizing amorphous silicon at low temperature, known as metal-induced crystallization, is disclosed in M. S. Haque, et al., J Appl. Phys., 79, 7529 (1996). The metal-induced crystallization crystallizes amorphous silicon by contacting amorphous silicon with a specific kind of metal which induces crystallization of silicon and then by carrying out annealing, enabling lower crystallization temperature.
In Ni-induced crystallization, crystallization is accelerated by NiSi2 which is the last phase of Ni silicide and works as a crystal nucleus, which is disclosed in C. Hayzelden, et al., Appl. Phys. Lett., 60, 225 (1992). As a matter of fact, NiSi2, which has a lattice constant of 5.406 xc3x85 similar to 5.430 xc3x85 of silicon, has the same structure as silicon. Thus, NiSi2 works as a crystal nucleus of amorphous silicon, accelerating crystallization to the direction  less than 111 greater than , disclosed in Tanemasa Asano, et al., Jpn. J Appl. Phys., Vol. 36, pp.1415-1419 (1997).
The metal-induced crystallization is affected by annealing time and temperature as well as quantity of metal. The crystallization time generally decreases as the quantity of metal increases.
Metal-induced crystallization has a low crystallization temperature, but unfortunately requires a long thermal processing time of over 20 hours at 500xc2x0 C. Therefore, this method still requires a high crystallization temperature as well as a long thermal process time.
As the quantity of metal increases, the metal-induced crystallization becomes more effective. However, intrinsic characteristics of a silicon layer are changed due to metal contamination in the crystallized silicon layer.
Generally, if the metal layer is formed on the amorphous silicon layer by using the sputtering method, it is difficult to reduce the amount of the metal material in the crystallized silicon layer. If the metal layer is formed on the amorphous silicon layer by using the coating method, it is possible to reduce the amount of the metal material applied to the crystallized silicon layer. However, the problem of the metal contamination could not be effectively solved.
Accordingly, when metal-induced crystallization is used, an improved method is required which reduces thermal treatment time, crystallization temperature, and metal contamination in a film.
Accordingly, the present invention is directed to a method of crystallizing an amorphous silicon layer and a crystallizing apparatus thereof that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
The object of the present invention is to provide a method of crystallizing an amorphous silicon layer and a crystallizing apparatus thereof which accelerate the crystallization of amorphous silicon by use of plasma while decreasing crystallization temperature.
Another object of the present invention is to provide a method of crystallizing an amorphous silicon layer and a crystallizing apparatus thereof which alleviate metal contamination in a crystallized silicon layer by controlling density and exposure time of plasma as well as forming metal-induced polysilicon on a glass substrate of a large area during a short period.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention includes the steps of depositing an inducing substance for silicon crystallization on an amorphous silicon layer by plasma exposure, and carrying out annealing on the amorphous silicon layer.
In another aspect, the present invention includes the steps of preparing a substrate on which an amorphous silicon layer is formed, depositing an inducing substance for silicon crystallization on the substrate by plasma exposure, and carrying out annealing on the substrate where the inducing substance is deposited.
In a further aspect, the present invention includes the steps of depositing an inducing substance for silicon crystallization on an amorphous silicon layer by plasma exposure as soon as annealing is carried out on the amorphous silicon layer.
In a further aspect, the present invention includes the steps of depositing an inducing substance for crystallization on an amorphous substance layer by plasma exposure, and carrying out annealing on the amorphous substance layer.
In a further aspect, the present invention includes the steps of depositing an inducing substance for crystallization on an amorphous substance layer by plasma exposure as soon as annealing is carried out on the amorphous substance layer.
In a further aspect, the present invention includes a chamber having inner space; a substrate support in the chamber, the substrate support supporting a substrate; a plasma generating means in the chamber, the plasma generating means producing plasma inside the chamber; and a heater at the substrate support, the heater supplying the substrate with heat.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.